hardMultiple Choice
300-410 Practice Question: Is troubleshooting an OSPFv2 issue where a router…
A network engineer is troubleshooting an OSPFv2 issue where a router R1 is not receiving a specific route for 10.0.0.0/8 from a neighbor R2. The adjacency is FULL, and 'show ip ospf database' on R1 shows the LSA for 10.0.0.0/8 as a type 5 LSA. However, the route is not in the routing table. 'show ip route 10.0.0.0' shows no route. What is the most likely cause?
⚠ Common exam trap
300-410 often tests the misconception that if an LSA is in the OSPF database, the route must be in the routing table, ignoring filtering mechanisms like distribute-lists that act at route installation.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The router R1 has a distribute-list applied to the OSPF process that filters the route 10.0.0.0/8.
A distribute-list applied to the OSPF process on R1 can filter the route even though the LSA is present in the OSPF database. The LSA is received and stored (so it appears in 'show ip ospf database'), but the distribute-list prevents it from being installed in the routing table, which matches the symptom of a type 5 LSA present but no route.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The router R1 has a distribute-list applied to the OSPF process that filters the route 10.0.0.0/8.
Why this is correct
A distribute-list filters routes when installing them into the routing table, so the type 5 LSA still appears in the OSPF database while the route is suppressed. This matches the FULL adjacency and populated LSDB with an empty routing table.
- ✗
The route is a type 5 LSA, but the router is in a stub area.
Why it's wrong here
A stub area cannot carry type 5 LSAs at all, so R1 would never show one in its database; the ABR instead injects a default type 3 summary. Seeing a type 5 LSA proves the area is not stub. Stub areas suit networks wanting to shrink LSDB size by blocking external LSAs.
- ✗
The router has a higher administrative distance for OSPF routes, causing it to prefer another routing protocol.
Why it's wrong here
Administrative distance only breaks ties between protocols that both installed the prefix; a type 5 LSA present in the database with no competing route means the route was never accepted, so AD is irrelevant here. AD comparison applies when the same prefix arrives via OSPF and EIGRP simultaneously.
- ✗
The route has a metric of 16777214, which is considered infinite.
Why it's wrong here
A metric of 16777214 (LSInfinity) still installs the route, marked unreachable, so 'show ip route' would display it rather than nothing. Its absence means the LSA was never eligible for SPF calculation. LSInfinity is used during graceful shutdown or route poisoning to withdraw a prefix.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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Same concept, more angles
1 more way this is tested on 300-410
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer is troubleshooting an OSPFv3 issue where a router R1 is not learning routes from a neighbor R2. The adjacency is FULL, but 'show ipv6 route ospf' on R1 shows only a default route. R2 is an ASBR redistributing connected routes into OSPFv3. 'show ipv6 ospf database external' on R1 shows the external routes, but they are not installed in the routing table. What is the most likely cause?
hard- ✓ A.The router R1 has a distribute-list in the OSPFv3 process that filters out the external routes.
- B.The external routes have a metric of 16777214, which is considered infinite.
- C.The router R1 does not have IPv6 unicast routing enabled.
- D.The external routes are type 5 LSAs but the router is in a totally stubby area.
Why A: The external routes are present in the OSPFv3 database but not installed in the routing table, which indicates a policy filtering them out. A distribute-list applied to the OSPFv3 process can filter routes from being installed. Since the adjacency is FULL and LSAs are received, the issue is local to R1's route installation.
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.